1. Field of the Invention
This invention relates to mammals into which foreign DNA has been introduced, thereby generating transgenic mammals. More specifically, the invention concerns generation of transgenic mammals that have a decreased platelet count, megakaryocyte leukemia, or both conditions.
2. Description of Related Art
Production of transgenic mammals involves the insertion of novel nucleic acid sequences into one or more chromosomes of the mammal. The DNA is typically delivered to the pronucleus of an egg where it is incorporated into the DNA of the embryo. This embryo is then implanted into a "surrogate host" for the duration of gestation. The offspring of the surrogate host are evaluated for the presence of the novel nucleic acid sequence(s).
Expression of the novel DNA sequence(s), or transgene(s), can confer a new phenotype on the mammal. Depending upon the nucleic acid sequence(s) inserted and the level of expression in the mammal, the mammal may become more or less susceptible to a particular disease or series of diseases. Such transgenic mammals are valuable for in vivo screening and testing of compounds that may be useful in treating or preventing the disease(s), and/or for developing methods useful in diagnosing the disease.
Transgenic mammals have been described in the art. Wagner et al., U.S. Pat. No. 4,873,191 teach mammals containing exogenous DNA which has been introduced by microinjection of the DNA into a mammalian zygote.
Leder et al., U.S. Pat. No. 4,736,866, teach a transgenic mammal whose germ and somatic cells contain an activated oncogene sequence introduced into the mammal, or its ancestors, early in development (the one-cell or fertilized embryo stage). Such transformation results in the animal having a greater than normal chance of developing neoplasms.
Evans et al., U.S. Pat. No. 4,870,009, teach production of certain mammalian hormones by insertion of a DNA construct into fertilized mammalian eggs and implanting the fertilized eggs into a host mother for gestation. The DNA construct comprises a mammalian metallothionein gene promoter sequence fused to the mammalian hormone sequence of interest. The blood of the transformed mammals then is collected and the hormone of interest is isolated.
Noble et al., WO 91/13150, published Sep. 5, 1991, and Jat et al., Proc. Nat'l. Acad. Sci. USA, 88:5096-5100 [1991], teach production of mice with a DNA construct that contains a mutant SV40 large T antigen gene (the SV40 tsA58 mutant) linked to a major histocompatibility complex I promoter (H-2Kb). The specific promoter is used to facilitate expression of the transgene in a wide variety of tissues, and is induced by certain interferons. These mice are used as a source for generating transformed cell lines.
Leder et al., U.S. Pat. No. 5,175,383, describe a male transgenic mouse expressing the int-2 gene in urogenital tissues resulting in benign prostatic hyperplasia or hypertrophy.
Krimpenfort et al., U.S. Pat. No. 5,175,384, describe a transgenic mouse with a decreased level of mature T-cells.
Wagner et al., U.S. Pat. No. 5,175,385, describe a transgenic mouse expressing the human beta-interferon gene.
Ravid et al., Proc. Nat'l. Acad. Sci. USA, 85:1521-1525 [1991], discuss mice containing a transgene construct containing the platelet factor 4 promoter ("PF4") linked to the beta-galactosidase gene, and Ravid et al., Mol. Cell Biol., 11:6116-6127 [1991], teach various domains of the PF4 promoter.
Palmiter et al., Nature 316:457-460 [1985], teach the formation of choroid plexus tumors in mice that contain the DNA sequence for the 72 base-pair repeat SV40 enhancer and large-T antigen. When the SV40 enhancer element is not included in the DNA construct, other pathologies are observed as well.
Brinster et al., Cell 37:367-79 [1984], teach production of mice with a construct containing the SV40 early region genes and a metallothionein fusion gene. Several of the mice developed choroid plexus tumors, and/or thymic hypertrophy.
Thrombocytopenia, a decreased level of platelets in the blood relative to normal levels for a given mammalian species, affects the blood clotting ability of afflicted individuals. One manifestation of this disorder is increased bleeding. In addition, thrombocytopenia is a common side effect in patients receiving chemotherapy. The only currently available method for treating the disorder is platelet transfusion, a difficult and inherently risky procedure.
Jackson, Blood Cells, 15:237-253 [1989] describes a rat strain with a reduced platelet number.
Peters et al., Blood, 76:745-754 [1990] describe an autosomal recessive mutation in mice that confers combined anemia and thrombocytopenia on afflicted mice.
Megakaryocyte leukemia is a condition characterized by production of cancerous cells that have phenotypic traits resembling megakaryocytes. Such leukemia is currently treated by bone marrow transplants.
In view of the devastating effects of thrombocytopenia and megakaryocyte leukemia, there is a need in the art for suitable animals that provide in vivo model systems for studying the diseases and compounds that can be used to treat and/or prevent the diseases.
Accordingly, it is an object of the invention to provide a transgenic mammal that has a genotype which confers an increased proclivity towards thrombocytopenia and/or megakaryocyte leukemia as compared to a non-transgenic mammal. Such mammals are useful in screening compounds for treating these diseases, and for other purposes.
It is a further object herein to provide methods for preparing, and to prepare transgenic mammals containing such genotypes.
Other such objects will readily be apparent to one of ordinary skill in the art.